Doppler compensation for non-terrestrial network

ABSTRACT

Various arrangements for compensating for Doppler shift on a non-terrestrial orthogonal frequency division multiplex (OFDM) network are presented. A received frequency of a downlink satellite message received from a satellite may be determined. A downlink frequency delta between an expected frequency of the downlink satellite message and the received frequency of the downlink satellite message can be calculated. An uplink frequency delta based on the calculated downlink frequency delta may be calculated. An uplink transmission frequency at which an uplink OFDM symbol is transmitted may be calculated based on the calculated uplink frequency delta.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/401,528, filed on May 2, 2019, entitled “Doppler Compensation For ANon-Terrestrial Network,” the disclosure of which is hereby incorporatedby reference in its entirety for all purposes.

BACKGROUND

The amount of Doppler shift introduced to an electromagnetic signal canbe defined by Equation 1.

$\begin{matrix}{{\Delta\; F} = {F_{0}*v*\frac{\cos(\theta)}{c}}} & {{Eq}.\mspace{14mu} 1}\end{matrix}$

In Equation 1, the change in frequency (ΔF) is equal to the nominalcarrier frequency (F₀), multiplied by the relative velocity component ofthe objects receiving and transmitting an electromagnetic signal towardor away from each other, multiplied by the cosine of the angle betweenthe objects divided by the speed of light. The greater the carrierfrequency, the greater the change in frequency that will be caused byDoppler shift. Additionally, the greater the velocity, the greater thechange in frequency.

The amount of Doppler shift introduced at lower frequencies and when aninstance of user equipment, such as a cellular phone, is communicatingwith a stationary base station is relatively small and may not have ameaningful effect on frequency. However, at higher frequencies and insituations where the UE is moving at a high velocity (e.g., on ahigh-speed train or airplane), the amount of Doppler shift may no longerbe negligible.

SUMMARY

Various arrangements for compensating for Doppler shift on anon-terrestrial network, such as an orthogonal frequency divisionmultiplex (OFDM) network are presented herein. A user equipment (UE)instance may determine an absolute location of the UE instance. An anglebetween the UE instance and a satellite of the non-terrestrial OFDMnetwork may be determined. A relative velocity of the UE instance may bedetermined with respect to a satellite of the non-terrestrial OFDMnetwork. A frequency delta may be determined based on: a nominal uplinkcarrier frequency, the relative velocity, and the angle. A transmissionfrequency may be adjusted at which an uplink OFDM symbol is to betransmitted to the satellite of the non-terrestrial OFDM network usingthe frequency delta. The UE instance may transmit the uplink OFDM symbolat the adjusted transmission frequency.

Embodiments of such arrangements may include one or more of thefollowing features: Determining the relative velocity of the UE instancewith respect to the satellite of the non-terrestrial OFDM network caninclude determining a velocity of the UE instance with respect to theEarth using global navigation satellite system (GNSS) measurements. Thesatellite may be in a low earth orbit (LEO) or middle earth orbit (MEO).Determining the relative velocity of the UE instance with respect to thesatellite of the non-terrestrial OFDM network can include accessing dataindicative of an orbit and orbital velocity of the satellite. Thesatellite can be in a geostationary orbit. A frequency of a downlinkOFDM symbol received from the satellite of the non-terrestrial OFDMnetwork can be measured. A frequency shift between an expected downlinkfrequency and the measured frequency of the downlink OFDM symbolreceived from the satellite of the non-terrestrial OFDM network can bedetermined. Adjusting the transmission frequency at which the uplinkOFDM symbol is to be transmitted to the satellite of the non-terrestrialOFDM network may be further based on the determined frequency shiftbetween the expected downlink frequency and the measured frequency ofthe downlink OFDM symbol received from the satellite of thenon-terrestrial OFDM network. The UE instance can communicate with thesatellite of the non-terrestrial OFDM network using a 5G New Radio (NR)radio access technology (RAT). The UE instance may be a smartphone.

BRIEF DESCRIPTION OF THE DRAWINGS

A further understanding of the nature and advantages of variousembodiments may be realized by reference to the following figures. Inthe appended figures, similar components or features may have the samereference label. Further, various components of the same type may bedistinguished by following the reference label by a dash and a secondlabel that distinguishes among the similar components. If only the firstreference label is used in the specification, the description isapplicable to any one of the similar components having the same firstreference label irrespective of the second reference label.

FIG. 1 illustrates an embodiment of an instance of UE moving relative toa satellite of a non-terrestrial network.

FIG. 2 illustrates an embodiment of an instance of UE that alterstransmission frequency to compensate for Doppler shift.

FIG. 3 illustrates an embodiment of a method for an instance of UE tocompensate for Doppler Shift.

FIG. 4 illustrates another embodiment of a method for an instance of UEto compensate for Doppler Shift based on the amount Doppler shiftmeasured in a downlink signal.

FIG. 5 illustrates an embodiment of a method for a UE instance tocompensate for Doppler shift based on the amount Doppler shift measuredin a downlink signal and a frequency delta based on calculated velocity,position, and angle.

DETAILED DESCRIPTION

Orthogonal Frequency Divisional Multiplex (OFDM) is a form of digitalsignal modulation that allows narrowband channels to exist on subcarrierfrequencies without guard bands being present between the subcarriers.For OFDM signal modulation to function properly, it is important fordevices to precisely transmit on their allocated subcarrier frequenciesin order to reduce interference and cross-talk among subcarrierfrequencies. Avoiding such interference and cross-talk at lowfrequencies and when the devices communicating with each other arestationary or nearly stationary may not need to take into account theDoppler effect. However, as frequency and relative velocity increases,the Doppler effect can have a significant effect on the frequency.

In a non-terrestrial network (NTN), communication may occur between auser equipment (UE) instance and a satellite. If the satellite is ingeostationary orbit, the satellite can effectively be treated as beingstationary. However, the UE may be moving, possibly quickly. Forinstance, the UE may be temporarily located or permanently installed ona high-speed train or an airplane. For instance, UE may be used toprovide WiFi to passengers so that they can access the Internet andother network-based services. If the satellite is in a non-geostationaryorbit (e.g., LEO or MEO), the relative velocity component between the UEand the satellite may be significantly increased due to the orbit of thesatellite around the earth. As a simple example, referring to Equation1, at 30 GHz at LEO satellite's orbit may contribute a Doppler shift of720 kHz.

A UE instance may be able to determine its location and velocity, suchas using a global navigation satellite system (GNSS). The UE may furtherhave access to data indicative of the location and orbit of a satellite.The UE may be able to determine the angle between the UE and thesatellite and determine a relative velocity component either toward oraway from the satellite along the Earth's surface. The UE may then beable to calculate the amount frequency shift that will be caused by theDoppler effect. The UE may then adjust its uplink transmissionfrequency, such as for the transmission of OFDM symbols, to compensatefor the Doppler effect.

Additionally or alternatively, the UE instance may be able to comparethe received frequency of a downlink signal from the satellite to anexpected frequency. The different in frequency may be attributed to theDoppler effect. Using this change in frequency, the UE may be able tocalculate the change in frequency that the Doppler effect will affect anuplink transmission, which may occur on a different frequency. Thischange in frequency can be combined with (e.g., averaged) with thechange in frequency calculated based on position, velocity, and angle ormay be used in lieu of this calculation.

FIG. 1 illustrates an embodiment of a system 100 of UE instances 110moving relative to a satellite 120 of a non-terrestrial network. Thenon-terrestrial network may use OFDM and may allow for bidirectionalcommunication with the UE instance. In some embodiments, thenon-terrestrial network may be a 5G NR (New Radio) network. In variousembodiments, satellite 120 may be in geosynchronous orbit or may be inLEO or MEO. UE instances 110 (110-1, 110-2) may move in variousdirections approximately along the surface of Earth 101 relative tosatellite 120. (While two UE instances 110 are illustrated, this numberof UE is for example purposes only. A much greater number of UE may becommunicating with satellite 120 in real-world implementations.) UEinstances 110 may be smartphones, cellphones, tablet computers, or othercomputerized devices that communicate with a satellite that is part of aNTN. In some embodiments, a UE instance may be used to provide multipleother users with network access. For instance, mass-transit, such as atrain or airplane, may have UE installed that enables WiFi or anotherform of network access for a large number of people. Such communicationmay be performed using 5G New Radio (NR) radio access technology (RAT).In an embodiment in which satellite 120 is in a geosynchronous orbit,satellite 120 can be treated as being stationary. In such embodiments,Doppler shift in uplink transmissions (that is, data transmissions frominstances of UE to satellite 120) can be wholly attributed to movementof the particular UE instance. For example, if UE instance 110-1 ismoving 600 km/hr west, it could result in a significant amount ofDoppler shift in uplink communications compared to UE instance 110-2that is moving 100 km/hr east.

Each of UE instances 110 may be capable of determining its absolutelocation. For instance, a global navigation satellite system (GNSS)module may be on-board each UE instance. Such a GNSS module may use theGlobal Positioning System (GPS), GLONASS, Galileo, Beidou, and/or othersome other form of positioning system. Each UE instance may: 1) haveaccess to data indicative of the location of satellite 120; 2) be ableto determine its absolute location using the GNSS module; and 3) be ableto determine its absolute speed (relative to the surface of the earth)such as using multiple GNSS measurements. Using this information, eachUE instance can determine: 1) a relative velocity component indicativeof velocity toward or away from the satellite along the earth's surface;and 2) angle 131. Angle 131 represents the difference between the uplinkcommunication path 130 and approximately the earth's 101 surface (or,the direction to point 135, which is on the Earth's 101 surface directlybelow satellite 120. Angle 131 can be used as part of Equation 1. Forinstance, since UE instance 110-1 is displaced (distance 132) a greaterdistance from satellite 120 along the earth's 101 surface than UE 110-2(distance 142), the movement of UE instance 110-1 can have a greatereffect on Doppler shift than the movement of UE instance 110-2.

In a first set of embodiments, satellite 120 is in geostationary orbit.Therefore, each UE instance can calculate the amount of frequency shiftbased on the UE instance's: absolute location, relative velocitycomponent toward or away from the satellite along the earth's surface,and the satellite's location. In a second set of embodiments, satellite120 is in LEO or MEO orbit. In such embodiments, the orbit and velocityof satellite 120 needs to be taken into account to determine the amountof Doppler shift that the satellite's orbit around earth 101 will affectthe uplink transmission. For instance, if velocity 111 of UE instance110-1 is directly away from satellite 120 along earth's 101 surface andsatellite 121 is moving in opposite direction of velocity 121, there canbe significantly more Doppler shift on uplink transmissions than uplinktransmissions from UE instance 110-2, which may be travelling atvelocity 112 (which can be the same speed in an opposite direction asvelocity 111). Since velocity 112 is in the same direction of velocity121 of satellite 120, the velocities may partially cancel out theDoppler effect. UE instance 110-1 may determine a velocity componenttoward or away from point 135.

FIG. 2 illustrates an embodiment of an instance of UE that alterstransmission frequency to compensate for Doppler shift. The illustratedUE instance is UE instance 110-1 from FIG. 1. Other instances of UE mayinclude the same or similar components. UE instance 110-1 may include:processing system 210; satellite orbit data 215; GNSS receiver 220;frequency controller 230; receiver 240; transmitter 250; and Dopplershift analyzer 260. Processing system 210 may include one or moreprocessors. Processing system 210 may include one or morespecial-purpose or general-purpose processors. Such special-purposeprocessors may include processors that are specifically designed toperform the functions detailed herein. Such special-purpose processorsmay be ASICs or FPGAs which are general-purpose components that arephysically and electrically configured to perform the functions detailedherein. Such general-purpose processors may execute special-purposesoftware that is stored using one or more non-transitoryprocessor-readable mediums, such as random access memory (RAM), flashmemory, a hard disk drive (HDD), or a solid state drive (SSD).

Processing system 210 may receive absolute position measurements fromGNSS receiver 220 relative to Earth 101. Based on the absolute positionmeasurements, processing system 210 may determine a velocity (which canbe indicative of a speed and direction) of the instance of the UErelative to the Earth's surface. Processing system 210 may have accessto a non-transitory processor-readable medium, which may store satelliteorbit data 215. Satellite orbit data 215 may store the location of ageosynchronous satellite. Satellite orbit data 215 may store orbitalinformation for LEO and/or MEO satellites that allows processing system210 to calculate the current location and velocity of the satellite towhich the uplink transmission is to be sent. Processing system 210 mayuse Equation 1 to calculate the amount of Doppler shift caused bymovement of UE instance 110-1 and the satellite to which the uplinktransmission is to be transmitted. The amount that frequency is to beadjusted (the frequency delta) or a modified carrier frequency may beoutput by processing system 210 to frequency controller 230. Frequencycontroller 230 may be configured to control the frequency at whichuplink transmissions, such as OFDM symbols, are transmitted bytransmitter 250.

Doppler shift analyzer 260 may receive downlink transmissions from thesatellite via receiver 240. Receiver 240 may expect to receive downlinktransmissions on a particular frequency. However, due to Doppler shiftcaused by movement of the satellite and/or UE instance 110-1, thedownlink transmission may be received on a different frequency. Dopplershift analyzer 260 may determine the difference in frequency (orfrequency delta) between the expected frequency on which the downlinktransmission is to be received and the actual frequency at which thedownlink transmission is received.

Processing system 210 may use the frequency delta observed by Dopplershift analyzer 260 in addition to or instead of the calculated Dopplershift. For instance, in some embodiments, the change in frequencydetermined by Doppler shift analyzer 260 may be averaged by processingsystem 210 with the calculated change in frequency. In otherembodiments, processing system 210 may select between using the changein frequency received from Doppler shift analyzer 260 and the calculatedchange in frequency based on observed conditions. Feedback may bereceived from the satellite that indicates how well uplink datatransmitted by UE instance 110-1 is compensating for the Doppler shift.If the uplink transmission has a sufficient error in frequencycorrection, processing system 210 may switch or adjust how it is usingthe change in frequency determined by Doppler shift analyzer 260 and thecalculated change in frequency to compensate for the Doppler shift.

The Doppler shift on downlink communications may tend to cause lessinterference than the Doppler shift on uplink transmissions. Since allof the downlink transmissions originate from the same source (i.e., thesatellite), each UE instance will observe all downlink transmissionsshifted in the frequency domain. Since all downlink transmissions areshifted in the frequency domain, little or no interference among suchdownlink transmissions occurs.

FIG. 3 illustrates an embodiment of a method 300 for an instance of UEto compensate for Doppler Shift. Method 300 may be performed by a UEinstance, such as UE instance 110-1. The UE instance may includecomponents as detailed in relation to FIG. 2. At block 305, a UEinstance may determine its absolute location with respect to the Earth.This absolute position may be determined using a GNSS component.

At block 310, a relative velocity component of the UE instance withrespect to the satellite with which the UE instance is about to or isalready communicating may be determined or calculated. The relativevelocity component can represent the velocity toward or away from apoint on Earth directly below the satellite's location. If the satellitehas a geosynchronous orbit, the satellite may be treated as beingstationary. If the satellite is in a LEO or MEO orbit, the relativevelocity component of the satellite towards or away from the UE instancemay be added to (if in opposite directions) or subtracted from (if inthe same direction) the UE's velocity component to determine a relativevelocity component.

At block 315, an angle between the UE instance and the satellite may bedetermined. The angle may be between a direct path to the satellite(e.g., uplink communication path 130) and the point on the earth'ssurface directly below the satellite (e.g., point 135 in FIG. 1). Thesmaller the angle, the greater the effect of the relative velocitycomponent of the Doppler shift on uplink transmissions as received bythe satellite. To determine the angle, the location of the satellite maybe needed by the UE instance. The UE instance may access locally-storedsatellite orbit data or may access stored satellite data from a remotesource, such as via a network.

At block 320, a frequency delta may be calculated by the UE instanceusing Equation 1. Equation 1 may be calculated by the UE instance using:use the relative velocity component at which the satellite and the UEare either moving towards or away from each other and the anglecalculated at block 315 to determine a frequency delta.

At block 325, the transmission frequency at which an uplink datatransmission, such as in OFDM symbol, is to be transmitted may bealtered using the frequency delta. The frequency delta may be used toeither increase the transmission frequency or decrease the transmissionfrequency. The transmission frequency may be increased if the relativevelocity component indicates that the UE instance and satellite aremoving away from each other; and the transmission frequency may bedecreased if the relative velocity component indicates that the UEinstance and satellite are moving toward each other.

At block 330, the uplink OFDM symbol may be transmitted using theadjusted transmission frequency. By the frequency having been adjustedusing the calculated frequency delta, when the subcarrier on which theOFDM symbol was transmitted is received by the satellite, the Dopplershift may be compensated for such that little to no interference withother subcarrier transmissions by other instances of UE occurs.Therefore, the satellite may effectively receive the uplink transmissionat the nominal subcarrier frequency (without any perceived Dopplershift).

FIG. 4 illustrates another embodiment of a method for an instance of UEto compensate for Doppler Shift based on the amount Doppler shiftmeasured in a downlink signal. Method 400 may be performed by a UEinstance, such as UE instance 110-1. The UE instance may includecomponents as detailed in relation to FIG. 2. Method 400 may beperformed instead of or in addition to method 300. At block 401, adownlink signal may be received from a satellite. At block 405, thereceived frequency of the downlink signal may be determined by the UEinstance. At block 410, the UE instance may determine the frequency atwhich it expected to receive the downlink signal. For instance, thedownlink message may include data indicating the frequency at which thedata was transmitted or the UE instance may have data stored indicatingthe frequency at which downlink data is transmitted by the satellite. Atblock 415, a frequency delta between the expected frequency and thereceived frequency may be calculated by the UE instance.

Using Equation 2, which is equivalent to Equation 1, the value of

$\left( {v*\frac{\cos(\theta)}{c}} \right)$can be determined using the frequency delta determined at block 415 andthe nominal carrier frequency.

$\begin{matrix}{\left( {v*\frac{\cos(\theta)}{c}} \right) = \frac{\Delta\; F}{F_{0}}} & {{Eq}.\mspace{14mu} 2}\end{matrix}$

Using the value of

$\left( {v*\frac{\cos(\theta)}{c}} \right)$calculated from Equation 2, Equation 1 can then be re-evaluated usingthe nominal carrier frequency for the uplink OFDM symbol transmission todetermine the frequency delta to compensate for the Doppler shift of theuplink transmission at block 420. Since the value of

$\left( {v*\frac{\cos(\theta)}{c}} \right)$is based on an actual downlink transmission, the value may be moreaccurate than if calculated by the UE instance based on a determinedrelative velocity component and determined angle. Further, in suchembodiments, the UE instance may not need to determine its own velocityor absolute position.

At block 425, the transmission frequency at which an uplink datatransmission, such as an OFDM symbol, is to be transmitted may bealtered using the frequency delta calculated at block 420. The frequencydelta may be used to either increase the transmission frequency ordecrease the transmission frequency. The transmission frequency may beincreased if the relative velocity component indicates that the UEinstance and satellite are moving away from each other; and thetransmission frequency may be decreased if the relative velocitycomponent indicates that the UE instance and satellite are moving towardeach other. At block 425, the uplink transmission, such as an OFDMsymbol, may be transmitted using the adjusted transmission frequency. Bythe frequency having been adjusted using the calculated frequency deltabased on the measured Doppler shift of the downlink transmission, theDoppler shift may be compensated for such that little to no interferencewith other subcarrier transmissions by other instances of UE occurs.

FIG. 5 illustrates an embodiment of a method for a UE instance tocompensate for Doppler shift based on the amount Doppler shift measuredin a downlink signal and a frequency delta based on calculated velocity,position, and angle. At block 505, a UE instance may determine itsabsolute location with respect to the Earth. This absolute position maybe determined using a GNSS component.

At block 510, a relative velocity component of the UE instance withrespect to the satellite with which the UE instance is about to or isalready communicating may be determined or calculated. The relativevelocity component can represent the velocity toward or away from apoint on Earth directly below the satellite's location. If the satellitehas a geosynchronous orbit, the satellite may be treated as beingstationary. If the satellite is in a LEO or MEO orbit, the relativevelocity component of the satellite towards or away from the UE instancemay be added to (if in opposite directions) or subtracted from (if inthe same direction) the UE's velocity component to determine a relativevelocity component.

At block 515, an angle between the UE instance and the satellite may bedetermined. The angle may be between a direct path to the satellite(e.g., uplink communication path 130) and the point on the earth'ssurface directly below the satellite (e.g., point 135 in FIG. 1). Thesmaller the angle, the greater the effect of the relative velocitycomponent of the Doppler shift on uplink transmissions as received bythe satellite. To determine the angle, the location of the satellite maybe needed by the UE instance. The UE instance may access locally-storedsatellite orbit data or may access stored satellite data from a remotesource, such as via a network.

At block 520, a first frequency delta may be calculated by the UEinstance using Equation 1. Equation 1 may be calculated by the UEinstance using: use the relative velocity component at which thesatellite and the UE are either moving towards or away from each otherand the angle calculated at block 515 to determine a frequency delta.

At block 525, a downlink signal may be received from a satellite. Atblock 530, the received frequency of the downlink signal may bedetermined by the UE instance. At block 535, the UE instance maydetermine the frequency at which it expected to receive the downlinksignal. For instance, the downlink message may include data indicatingthe frequency at which the data was transmitted or the UE instance mayhave data stored indicating the frequency at which downlink data istransmitted by the satellite. At block 540, a downlink frequency deltabetween the expected frequency and the received frequency may becalculated by the UE instance.

At block 545, using Equation 2 as detailed in relation to method 400,the value of

$\left( {v*\frac{\cos(\theta)}{c}} \right)$can be used to calculate Equation 1 for the nominal carrier frequencyfor the uplink OFDM symbol transmission to determine the secondfrequency delta to compensate for the Doppler shift of the uplinktransmission.

At block 550, either the first frequency delta or the second frequencydelta is selected to use to adjust the uplink transmission frequency(e.g., of the OFDM symbol). In some embodiments, the first frequencydelta and the second frequency delta are averaged together or areotherwise combined. In some embodiments, a weighting is used. Forinstance, feedback may be occasionally received from the satellite thatindicates an amount of error in the frequency of uplink transmissionsfrom the UE instance. Based on the feedback data, the weighting of thefirst frequency delta compared to the second frequency delta can beadjusted. In other embodiments, the feedback data may indicate whetherthe calculated first frequency delta or the calculated second frequencydelta should be used to adjust uplink transmissions.

At block 555, the transmission frequency at which an uplink datatransmission, such as an OFDM symbol, is to be transmitted may bealtered using the combined frequency delta at block 550. The frequencydelta may be used to either increase the transmission frequency ordecrease the transmission frequency. The transmission frequency may beincreased if the relative velocity component indicates that the UEinstance and satellite are moving away from each other; and thetransmission frequency may be decreased if the relative velocitycomponent indicates that the UE instance and satellite are moving towardeach other. At block 560, the uplink transmission, such as an OFDMsymbol, may be transmitted using the adjusted transmission frequency. Bythe frequency having been adjusted using the calculated frequency deltabased on the measured Doppler shift of the downlink transmission, theDoppler shift may be compensated for such that little to no interferencewith other subcarrier transmissions by other instances of UE occurs.

The methods, systems, and devices discussed above are examples. Variousconfigurations may omit, substitute, or add various procedures orcomponents as appropriate. For instance, in alternative configurations,the methods may be performed in an order different from that described,and/or various stages may be added, omitted, and/or combined. Also,features described with respect to certain configurations may becombined in various other configurations. Different aspects and elementsof the configurations may be combined in a similar manner. Also,technology evolves and, thus, many of the elements are examples and donot limit the scope of the disclosure or claims.

Specific details are given in the description to provide a thoroughunderstanding of example configurations (including implementations).However, configurations may be practiced without these specific details.For example, well-known circuits, processes, algorithms, structures, andtechniques have been shown without unnecessary detail in order to avoidobscuring the configurations. This description provides exampleconfigurations only, and does not limit the scope, applicability, orconfigurations of the claims. Rather, the preceding description of theconfigurations will provide those skilled in the art with an enablingdescription for implementing described techniques. Various changes maybe made in the function and arrangement of elements without departingfrom the spirit or scope of the disclosure.

Also, configurations may be described as a process which is depicted asa flow diagram or block diagram. Although each may describe theoperations as a sequential process, many of the operations can beperformed in parallel or concurrently. In addition, the order of theoperations may be rearranged. A process may have additional steps notincluded in the figure. Furthermore, examples of the methods may beimplemented by hardware, software, firmware, middleware, microcode,hardware description languages, or any combination thereof. Whenimplemented in software, firmware, middleware, or microcode, the programcode or code segments to perform the necessary tasks may be stored in anon-transitory computer-readable medium such as a storage medium.Processors may perform the described tasks.

Having described several example configurations, various modifications,alternative constructions, and equivalents may be used without departingfrom the spirit of the disclosure. For example, the above elements maybe components of a larger system, wherein other rules may takeprecedence over or otherwise modify the application of the invention.Also, a number of steps may be undertaken before, during, or after theabove elements are considered.

What is claimed is:
 1. A method for compensating for Doppler shift on anon-terrestrial orthogonal frequency division multiplex (OFDM) network,the method comprising: receiving, by a user equipment (UE) instance; adownlink satellite message received from a satellite, wherein the UEinstance comprises: a transmitter, a receiver, and a processing systemthat comprises one or more processors; determining, by the UE instance,a received frequency of the downlink satellite message received from thesatellite; determining, by the UE instance, an expected frequency of thedownlink satellite message received from the satellite; calculating adownlink frequency delta between the expected frequency of the downlinksatellite message and the received frequency of the downlink satellitemessage; calculating an uplink frequency delta based on the calculateddownlink frequency delta; altering an uplink transmission frequency atwhich an uplink OFDM symbol is transmitted based on the calculateduplink frequency delta; and transmitting, by the UE instance, the OFDMsymbol at the altered uplink transmission frequency.
 2. The method forcompensating for Doppler Shift on the non-terrestrial OFDM network ofclaim 1, wherein calculating the uplink frequency delta based on thecalculated downlink frequency delta comprises determining a valueindicative of an angle between the satellite and the UE instance.
 3. Themethod for compensating for Doppler Shift on the non-terrestrial OFDMnetwork of claim 2, wherein calculating the uplink frequency delta basedon the calculated downlink frequency delta comprises calculating a valuefor ${v*\frac{\cos(\theta)}{c}},$ wherein v represents the relativevelocity of the UE instance to the satellite and c represents the speedof light.
 4. The method for compensating for Doppler Shift on thenon-terrestrial OFDM network of claim 1, wherein transmitting the OFDMsymbol at the altered transmission frequency compensates for the Dopplershift such that the satellite receives the OFDM symbol at a nominaluplink transmission frequency.
 5. The method for compensating forDoppler shift on the non-terrestrial OFDM network of claim 1, whereinthe satellite is in a low earth orbit (LEO) or middle earth orbit (MEO).6. The method for compensating for Doppler shift on the non-terrestrialOFDM network of claim 1, wherein the satellite is in a geostationaryorbit.
 7. The method for compensating for Doppler shift on thenon-terrestrial OFDM network of claim 1 wherein the UE instancecommunicates with the satellite of the non-terrestrial OFDM networkusing a 5G New Radio (NR) radio access technology (RAT).
 8. The methodfor compensating for Doppler shift on the non-terrestrial OFDM networkof claim 1 wherein the UE instance is a smartphone.
 9. The method forcompensating for Doppler shift on the non-terrestrial OFDM network ofclaim 1 wherein calculating an uplink frequency delta based on thecalculated downlink frequency delta is further based on a weighting oraveraging process being performed with a second frequency delta.
 10. Themethod for compensating for Doppler shift on the non-terrestrial OFDMnetwork of claim 9 wherein the second frequency delta is calculatedusing a different method.
 11. A system for compensating for Dopplershift on a non-terrestrial orthogonal frequency division multiplex(OFDM) network, the system comprising: a user equipment (UE) instance,comprising: a transmitter; a receiver; and a processing systemcomprising one or more processors, configured to: receive a downlinksatellite message received from a satellite; determine a receivedfrequency of the downlink satellite message received from the satellite;determine an expected frequency of the downlink satellite messagereceived from the satellite; calculate a downlink frequency deltabetween the expected frequency of the downlink satellite message and thereceived frequency of the downlink satellite message; calculate anuplink frequency delta based on the calculated downlink frequency delta;alter a transmission frequency at which an uplink OFDM symbol istransmitted based on the calculated uplink frequency delta; and causethe OFDM symbol to be transmitted at the altered transmission frequency.12. The system for compensating for Doppler shift on the non-terrestrialOFDM network of claim 11, wherein the processing system of the UEinstance being configured to calculate the uplink frequency delta basedon the calculated downlink frequency delta comprises the processingsystem being configured to determine a value indicative of an anglebetween the satellite and the UE instance.
 13. The system forcompensating for Doppler shift on the non-terrestrial OFDM network ofclaim 11, wherein the processing system of the UE instance beingconfigured to calculate the uplink frequency delta based on thecalculated downlink frequency delta comprises the processing systembeing configured to calculate a value for ${v*\frac{\cos(\theta)}{c}},$wherein v represents the relative velocity of the UE instance to thesatellite and c represents the speed of light.
 14. The system forcompensating for Doppler shift on the non-terrestrial OFDM network ofclaim 11, the system further comprising: the satellite, wherein thesatellite is part of the non-terrestrial OFDM network.
 15. The systemfor compensating for Doppler shift on the non-terrestrial OFDM networkof claim 14, wherein the processing system of the UE instance beingconfigured to cause the OFDM symbol to be transmitted at the alteredtransmission frequency compensates for the Doppler shift such that thesatellite receives the OFDM symbol at a nominal uplink transmissionfrequency.
 16. The system for compensating for Doppler shift on thenon-terrestrial OFDM network of claim 15, wherein the satellite receivesthe OFDM symbol at the nominal uplink transmission frequency.
 17. Thesystem for compensating for Doppler shift on the non-terrestrial OFDMnetwork of claim 14, wherein the satellite is in a low earth orbit (LEO)or middle earth orbit (MEO).
 18. The system for compensating for Dopplershift on the non-terrestrial OFDM network of claim 14, wherein thesatellite is in a geostationary orbit.
 19. The system for compensatingfor Doppler shift on the non-terrestrial OFDM network of claim 11wherein the UE instance communicates with the satellite of thenon-terrestrial OFDM network using a 5G New Radio (NR) radio accesstechnology (RAT).
 20. The system for compensating for Doppler shift onthe non-terrestrial OFDM network of claim 19 wherein the UE instance isa smartphone.